Project 1 is concerned with assessment and prediction of exposure of human and ecological receptors to contaminants in the environment. Our goals are to;i) determine how environmental fate and transport processes that act upon contaminants control the level and duration of potential exposure and, ii) develop useful methods and approaches to estimate exposure concentrations and, in collaboration with other Superfund projects, biological effects. Specific objectives include providing fundamental knowledge about the processes controlling the transport and transformation of contaminants, especially those related to complex mixtures;developing molecular-based and biosensor technologies and integrated tools for monitoring bioremediation and natural attenuation;and developing new models of reactive transport in groundwater and applying them to predict chemical exposure risks and remediation. We will consider three complex mixtures and their constituents as examples of Superfund-relevant and emerging issues related to fate, transport and transformation of contaminants in the environment. These include;i) biosolids from waste water treatment that contain pharmaceuticals, personal care and household products such as TCC/TCS and PBDEs, nanoparticles, and other chemicals of concern;ii) biofuels and fuel additives that include oxygenates;and iii) formulated pesticides such as pyrethroids. This grouping of compounds allows us to examine in a unique and integrated way the roles of particle size, surface characteristics, and co-occurring substances on contaminant fate and transport. Based on our research we will develop general principles and approaches that will be applicable to broader groups of contaminants not considered here and help predict emergence of new environmental contaminants.